<?php
class Student{
     function __construct() {
$this->surname = 'Shengyang';
$this->first_name = 'Xie';
$this->emails = array();
$this->grades = array();
}  

function add_email($which,$address) {
$this->emails[$which] = $address;
}
function add_grade($grade) {
$this->grades[] = $grade;
}

function average() {
$total = 0;
foreach ($this->grades as $value)
$total += $value;
return $total / count($this->grades);
}
function toString() {
$result = $this->first_name . ' ' . $this->surname;
$result .= ' ('.$this->average().")\n";
foreach($this->emails as $which=>$what)
$result .= $which . ': '. $what. "\n";
$result .= "\n";
return '<pre>'.$result.'</pre>';
}
}
   ?>